1. Field of the Invention
The present invention generally relates to a film forming technique and more particularly concerns a technique of forming a thin film by using concurrently a high-energy beam and a low-energy beam in combination.
2. Description of the Related Art
As the thin-film forming techniques, there have been known a variety of methods such as, for example, vacuum evaporation, sputtering, chemical vapor deposition, ion beam deposition, ion implantation and the others. In the vacuum evaporation process, a source material is vaporized under resistance heating or electron beam heating, whereby vaporized molecules (atoms) are deposited on a substrate. Energy of the particles (molecules, atoms) impinging on the substrate is primarily determined by thermal energy given by 3/2.multidot.kT where T represents the heating temperature in degrees Kelvin. According to the sputtering method, primary particles are caused to collide against a target to physically sputter the material constituting the target in the form of particles (molecules) which are then deposited on a substrate disposed in opposition to the target. Plasma sputtering in which plasma is used as a primary particle source is widely employed. By confining the plasma with a magnetron-type magnetic field, the sputtering rate can be increased. Although the particle beams for depositon by the process mentioned above have certain levels of energy, they are substantially incapable of sputtering the substrate-constituting molecules from the substrate surface.
In the ion beam deposition, ions are accelerated into an ion beam to irradiate a substrate, whereby ionized particles are deposited on the substrate. The ion beam comprises particles of an energy from several hundreds to several thousands electron volts. In ion implantation, ions are accelerated and implanted into a substrate. Thus, the particles (ions) usually have a considerably high energy (on the order of 1 KeV to 100 KeV). Particles of high energy injure the substrate as they are implanted into the substrate and sputter the same. For evading such sputter phenomenon, the ion accelerating energy may be lowered to the order of 100 eV.
These various film-forming techniques have respective shortcomings as well as advantages.
An attempt is reported according to which two kinds of techniques are combined to gain more satisfactory result.
Japanese Patent Application Laid-Open No. 2022/1983 (JP-A-NO. 58-2022) discloses a deposition method according to which a metal is evaporated for deposition by using a electron beam, while ions of a substance such as nitrogen, oxygen, hydrogen or the like which forms a metallic compound with the above-mentioned metals are caused to irradiate a film by using a mass-analyzed ion implanter. In this connection, it is reported that satisfactory result can be obtained when the ion beam is imparted with sufficiently high energy to bring about the sputter phenomenon.